FIGURE 6.

TGT-deficient animals have decreased levels of BH4 in plasma and elevated BH2 in plasma and urine. a, total biopterin; (b) BH4; (c) BH2 levels in the plasma; (d) total biopterin; (e) BH4; and (f) BH2 levels in the urine of wild-type (+/+), heterozygous (+/Gt), and homozygous (Gt/Gt) Qtrt1 gene-trap mice. Pterin levels were determined from concentration curves made using authentic standards. Each point represents the average value from triplicate measurements from 12 individual mice. ***, p < 0.001, analysis of variance, Dunnett's test.